1. Field of the Invention
This invention relates in general to an AGC window detector, and more particularly to an AGC window detector that determines whether a difference between input signals falls within a window.
2. Description of Related Art
Today""s wireless communications markets are being driven by a multitude of user benefits. Products such as cellular phones, cordless phones, pagers, and the like have freed corporate and individual users from their desks and homes and are driving the demand for additional equipment and systems to increase their utility. As a result digital radio personal communications devices will play an increasingly important role in the overall communications infrastructure in the next decade.
Mixed-signal integration and power management have taken on added importance now that analog and mixed analog-digital ICs have become the fastest-growing segment of the semiconductor industry. Integration strategies for multimedia consoles, cellular telephones and battery-powered portables are being developed, as well as applications for less integrated but highly specialized building blocks that serve multiple markets. These building blocks include data converters, comparators, demodulators, filters, amplifiers and voltage regulators.
One important aspect of digital radio personal communications devices is the integration of the RF sections of transceivers. Compared to other types of integrated circuits, the level of integration in the RF sections of transceivers is still relatively low. Considerations of power dissipation, low offset budgets, form factor, and cost dictate that the RF/IF portions of these devices evolve to higher levels of integration than is true at present. Nevertheless, there are some key barriers to realizing these higher levels of integration.
For example, most applications provide a comparator circuit in an RF receiver system to compare different signals. For AGC window detectors, input signals are compared to a reference voltage and a resulting signal is used to drive a digital logic circuits to achieve a desired gain. However, the information received from the AGC window detector determines parameters such as: signal level budget, minimum gain step size, amplifier voltage limits, speed of input level variations due to multi-path fading and demodulator dynamic range. Input signal level regulation is critical for these components. To provide this regulation, the window detector implements circuitry which compares a peak-to-peak amplitude of an in-phase and a peak-to-peak amplitude a quadrature input signal to the reference voltage. A reference voltage source generates a reference voltage window that is used to determine if a resulting amplitude of the in-phase and amplitude of the quadrature input signal is less than, greater than, or equal to the reference voltage.
It can be seen then that there is a need for an AGC window detector to determine whether the difference between input signals falls within a window.
It can also be seen that there is a need for a window detector that compares input signals and drives digital circuits in response thereto to produce the desired gain.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an AGC window detector that determines whether a difference between input signals falls within a window.
The present invention solves the above-described problems by providing an AGC window detector that determines whether the difference between input signals falls within a window by comparing input signals and driving digital circuits in response thereto to produce the desired gain.
A method in accordance with the principles of the present invention includes comparing a first input signal and a second input signal to a first reference voltage to produce a first output signal and comparing the first input signal and the second input signal to a second reference voltage to produce a second output signal, wherein the first and the second output signal indicates whether the difference of the first and second input signals are within a reference window defined by the first and the second reference voltages.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the method further includes computing the difference between the value of the first input and second input signal.
Another aspect of the present invention is that the computing the difference between the value of the first and second input signal further includes computing the difference between a maximum in-phase signal value with a minimum in-phase signal value and computing the difference between a maximum quadrature signal value with a minimum quadrature signal value resulting in a differential in-phase value of the input signals and a differential quadrature value of the input signals respectively.
Another aspect of the present invention is that wherein the computing the difference between the in-phase and quadrature signal further includes sampling the differential in-phase and quadrature signals.
Another aspect of the present invention is that the sampling of the differential in-phase and quadrature signal further includes computing an addition and a subtraction of the differential in-phase and quadrature signal voltages to determine a polarity of a resulting voltage.
Another aspect of the present invention is that the subtraction of the differential in-phase and quadrature voltage further includes reversing the polarity of the positive and negative components of the in-phase and quadrature signal.
Another aspect of the present invention is that the computing of the addition and the subtraction further includes sampling the differential in-phase and quadrature voltage via a parasitic insensitive sampling network comprising a capacitor.
Another aspect of the present invention is that the parasitic insensitive sampling further includes accomplishing the addition and the subtraction by a charge sharing of parallel capacitors.
Another aspect of the present invention is that the sampling of the differential in-phase and quadrature signal further includes preamplifying a low level signal.
Another aspect of the present invention is that the sampling of the differential in-phase and quadrature signal further includes latching a voltage level.
Another aspect of the present invention is that the sampling of the differential in-phase and quadrature signal further includes generating two nominally identical voltages to reduce cross talk in a preamplified low level signal.
Another aspect of the present invention is that the method further includes providing a reference voltage.
Another aspect of the present invention is that the providing of the reference voltage further includes generating all needed reference voltages from a single source.
Another aspect of the present invention is that the providing of the reference voltage further includes providing a control signal to regulate the reference voltage wherein the control signal varies a hysteresis window.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.